arXiv subjects

Soumitra SenGupta

Publications and source records attributed to Soumitra SenGupta.

At least 109 records · Page 6Linked to original sources

arXiv2012

Gauge and moduli hierarchy in a multiply warped braneworld scenario

A generalized Randall sundrum model in six dimensional bulk is studied in presence of non-flat 3-branes at the orbifold fixed points. The warp factors for this model is determined in terms of multiple moduli and brane cosmological constant. We show that the requirements of a vanishingly small cosmological constant on the visible brane along with non-hierarchical moduli, each with scale close to Planck length, lead to a scenario where the 3-branes can not have any intermediate scale and have energy scales either close to Tev or close to Planck scale. Such a scenario can address both the gauge hierarchy as well as fermion mass hierarchy problem in standard model. Thus simultaneous resolutions to these problems are closely linked with the near flatness condition of our universe without any intermediate hierarchical scale for the moduli.

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arXiv2012

On the origin of brane cosmological constant in two-brane warped geometry model

In the backdrop of generalised Randall-Sundrum braneworld scenario, we look for the possible origin of an effective four dimensional cosmological constant ($Ω_{vis}$) on the visible 3-brane due to the effects of bulk curvature and the modulus field that can either be a constant or dependent on extra dimensional co-ordinate $y$ or a time dependent quantity. In case of constant or $y$ dependent modulus field, the induced $Ω_{vis}$ leads to an exponentially expanding Universe. For such modulus fields the presence of vacuum energy densities on either of the 3-branes as well as a non-vanishing bulk curvature $l$ ($l \sim {Λ_5}^{-1}$) are essential to generate an effective $Ω_{vis}$. In particular for constant modulus field the Hubble constant turns out to be equal to the visible brane cosmological constant which agrees with the present result. In an alternative scenario, a time dependent modulus field is found to be capable of accelerating the Universe. The Hubble parameter in this case is determined for a slowly time-varying modulus field.

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arXiv2011

Fermion mass hierarchy in a multiple warped braneworld model

A geometric understanding of the origin of mass hierarchy among the standard model fermions have been addressed in a multiple warped spacetime. We show that the requirement of $10^{16}$ order warping between the Planck and the visible branes without creating any significant hierarchy among the moduli results into splitting of fermion masses in the standard model. Values of the various parameters of the extra dimensional model and the corresponding fermion masses are determined.

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arXiv2011

Soft supersymmetry breaking with tiny cosmological constant in flux compactified N=1 Supergravity

Using the flux compactification scenario in a generic supergravity model we construct a set of conditions which are necessary to generate de-Sitter or anti de-Sitter vacua for appropriate choices of the parameters in superpotential. It is shown that a mass spectrum consistent with softly broken TeV scale supersymmetry in a minimal supersymmetric standard model at the observable sector can be obtained along with a tiny cosmological constant when the Kahler and superpotential of the hidden sector satisfy a set of general constraints. Constructing a specific model with Kahler and superpotentials which satisfy the above constraints, it is demonstrated that all the hidden sector fields have vacuum expectation values close to Planck scale and the resulting low energy potential does not have any flat direction.

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arXiv2011

Cosmology and large mass hierarchy in multiply warped braneworld scenario

Hubble expansion in warped braneworld model is addressed in presence of more than one warped extra dimensions. It is shown that while the expansion depends on all the moduli, an exponential nature of the expansion of the scale factor emerges as a generic feature which is independent of the number of extra dimensions. Expression for the effective brane cosmological constant in such model has been derived. It is shown that similar to the 5-dimensional Randall-Sundrum model a fine tuning between the bulk cosmological constant and brane tension is required to obtain the desired cosmological constant on the brane. The length of the extra dimensions are determined in such scenario. Finally introduing pressureless matter in the bulk an observationally consistent cosmology was obtained on the visible brane.

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arXiv2011

Matter-gravity interaction in a multiply warped braneworld,

The role of a bulk graviton in predicting the signature of extra dimensions through collider-based experiments is explored in the context of a multiply warped spacetime. In particular it is shown that in a doubly warped braneworld model, the presence of the sixth dimension, results in enhanced concentration of graviton Kaluza Klein (KK) modes compared to that obtained in the usual 5-dimensional Randall-Sundrum model. Also, the couplings of these massive graviton KK modes with the matter fields on the visible brane turn out to be appreciably larger than that in the corresponding 5- dimensional model. The significance of these results are discussed in the context of KK graviton search at the Large Hadron Collider (LHC).

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arXiv2011

Bulk Higgs and Gauge fields in a multiply warped braneworld model

We readdress the problems associated with bulk Higgs and the gauge fields in a 5-dimensional Randall-Sundrum model by extending the model to six dimensions with double warping along the two extra spatial dimensions. In this 6-dimensional model we have a freedom of two moduli scales as against one modulus in the 5-dimensional model. With a little hierarchy between these moduli we can obtain the right magnitude for $W$ and $Z$ boson masses from the Kaluza-Klein modes of massive bulk gauge fields where the spontaneous symmetry breaking is triggered by bulk Higgs . We also have determined the gauge couplings of the standard model fermions with Kaluza-Klein modes of the gauge fields. Unlike the case of 5-dimensional model with a massless bulk gauge field, here we have shown that the gauge couplings and the masses of the Kaluza-Klein gauge fields satisfy the precision electroweak constraints and also obey the Tevatron bounds.

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arXiv2011

Low-scale SUSY breaking by modular fields and Higgs mass bounds

We consider a scenario where supersymmetry (SUSY) is broken at a relatively low scale by modular fields of extra compact spacelike dimensions. The effect of both soft and hard SUSY breaking terms on the mass of the lightest neutral Higgs boson are investigated. An important conclusion is that the lightest neutral Higgs can be considerably more massive than what is expected in the MSSM, if the overseeing theory breaks SUSY at a scale not too far above a TeV. An explicit model that implements this has been shown for illustration.

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arXiv2010

Antisymmetric tensor fields in a generalized Randall-Sundrum scenario

Bulk antisymmetric tensor fields of different ranks have been studied in the context of a generalized Randall-Sundrum model with a non-vanishing induced cosmological constant on the visible brane. It is shown that instead of the usual exponential suppression of the couplings of the zero modes of these bulk fields with the brane fermions in the original Randal-Sundrum model, here the couplings are proportional to the brane cosmological constant. Thus in an era of large cosmological constant these fields have significant role in physical phenomena because of their enhanced couplings with the visible brane fermions.

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arXiv2010

Bulk Higgs field in a Randall-Sundrum model with nonvanishing brane cosmological constant

We consider the possibility of Higgs mechanism in the bulk in a generalised Randall-Sundrum model, where a nonvanishing cosmological constant is induced on the visible brane. This scenario has the advantage of accommodating positive tension of the visible brane and thus ensures stability of the model. It is shown that several problems usually associated with this mechanism are avoided if some dimensionful parameters in the bulk are allowed to lie a little below the Planck mass. The most important of these is keeping the lowest massive mode in the scale of the standard electroweak model, and at the same time reducing the gauge coupling of the next excited state, thus ameliorating otherwise stringent phenomenological constraints.

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arXiv2010

Scalar Kaluza-Klein modes in a multiply warped braneworld

The Kaluza-Klein (KK) modes of a massive scalar field on a 3-brane embedded in six dimensional multiply warped spacetime are determined. Due to the presence of warping along both the extra dimensions the KK mass spectrum splits into two closely spaced branches which is a distinct feature of this model compared to the five dimensional Randall-Sundrum model. This new cluster of the KK mode spectrum is expected to have interesting phenomenological implications for the upcoming collider experiments. Such a scenario may also be extended for even larger number of orbifolded extra dimensions.

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arXiv2009

A critical analysis of thermodynamic properties of braneworld black holes in anti-de Sitter spacetime

Thermodynamic properties of Schwarzschild-Anti de-Sitter (Sch-AdS) and Reissner-Nordström-Anti de-Sitter (RN-AdS) blackholes in 3+1 dimensional spacetime are studied critically with special reference to the warped braneworld black holes with non-vanishing cosmological constant on the brane. Explicit dependence of the thermodynamic variables on the parameters of the braneworld model such as the induced three brane cosmological constant as well as the bulk cosmological constant have been determined. Hawking-Page phase transition has been discussed for both Sch-AdS and RN-AdS black holes. At the phase transition point it is shown that the parameters mass, charge and cosmological constant get correlated by an inequality relation which originates from the background warped geometry model.

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arXiv2009

Stable two--brane models with bulk tachyon matter

We explore the possibility of constructing stable, warped two--brane models which solve the hierarchy problem, with a bulk non--canonical scalar field (tachyon matter) as the source term in the action. Among our examples are two models--one with a warp factor (denoted as $e^{-2f(σ)}$) which differs from that of the standard Randall--Sundrum by the addition of a quadratic piece in the $f(σ)$ and another, where the warping is super-exponential. We investigate the issue of resolution of hierarchy and perform a stability analysis by obtaining the effective inter-brane potentials, in each case. Our analysis reveals that there does exist stable values of the modulus consistent with hierarchy resolution in both the models. Thus, these models, in which the bulk scalar field generates the geometry and also ensures stability, provide viable alternatives to the standard Randall--Sundrum two-brane scenario.

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arXiv2009

Neutrino masses, the cosmological constant and a stable universe in a Randall-Sundrum scenario

The Randall-Sundrum model of warped geometry in a five-dimensional scenario, aimed at explaining the hierarchy between the Planck and electroweak scales, is intrinsically unstable in its minimal form due to negative tension of the visible brane. A proposed solution to the problem yields a negative cosmological constant in four dimensions. We show that this wrong-sign cosmological constant is restricted to small values, therefore requiring less cancellation from hitherto unknown physics, if bulk neutrinos are postulated to explain the observed neutrino mass pattern. Thus neutrino masses, a stable Tev-brane configuration and new physics in the context of the cosmological constant get rather suggestively connected by the same thread.

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arXiv2009

A Randall-Sundrum scenario with bulk dilaton and torsion

We consider a string-inspired torsion-dilaton-gravity action in a Randall-Sundrum brane world scenario and show that, in an effective four-dimensional theory on the visible brane, the rank-2 antisymmetric Kalb-Ramond field (source of torsion) is exponentially suppressed. The result is similar to our earlier result in [12], where no dilaton was present in the bulk. This offers an explanation of the apparent invisibility of torsion in our space-time. However, in this case the trilinear couplings ~ Tev^{-1} between dilaton and torsion may lead to new signals in Tev scale experiments, bearing the stamp of extra warped dimensions.

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arXiv2009

Tunneling across dilaton-axion black holes

In this work we study both charged and uncharged particles tunneling across the horizon of spherically symmetric dilaton-axion black holes using Parikh-Wilczek tunneling formalism. Such black hole solutions have much significance in string theory based models. For different choices of the dilaton and axion couplings with the electromagnetic field, we show that the tunneling probability depends on the difference between initial and final entropies of the black hole. Our results, which agrees with similar results obtained for other classes of black holes, further confirm the usefulness of Parikh-Wilczek formalism to understand Hawking radiation. The emission spectrum is shown to agree with a purely thermal spectrum only in the leading order. The modification of the proportionality factor in the area-entropy relation in the Bekenstien-Hawking formula has been determined.

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arXiv2009

Kaluza-Klein modes of bulk fields in a generalized Randall-Sundrum scenario

We consider a generalised two brane Randall-Sundrum model with non-zero cosmological constant on the visible TeV brane. Massive Kaluza-Klein modes for various bulk fields namely graviton, gauge field and antisymmetric second rank Kalb-Ramond field in a such generalized Randall-Sundrum scenario are determined. The masses for the Kaluza-Klein excitations of different bulk fields are found to depend on the brane cosmological constant indicating interesting consequences in warped brane particle phenomenology

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arXiv2009

Fermion localization in generalised Randall Sundrum model

A generalized two-brane Randall-Sundrum warped braneworld model admits of solutions of the warp factor for both positive or negative cosmological constant on the visible 3-brane which can resolve the naturalness problem in connection with the fine tuning of Higgs mass in the standard model of elementary particles. To explore the location of the standard model fermions in such a generalized warped model, we, in this work, determine the dependence of the localization profile of a bulk fermion on the brane cosmological constant brane tension and the bulk fermion mass. Our results reveal that for a positive and small value of the induced cosmological constant a bulk fermion is localized close to the brane. On the other hand for a visible brane with negative cosmological constant and positive tension, the fermions are localized inside the bulk leading to phenomenologically interesting possibilities.

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